Milk fat globules—A natural carrier for exogenous lipophilic bioactives

Abstract

Encapsulation using naturally occurring and pre-formed carriers has been of interest for food, agricultural, cosmetic, and medical applications in recent years. This study evaluated the feasibility of using milk fat globules (MFGs) as natural carriers for exogenous lipophilic bioactives. Five compounds of varying hydrophobicity (octanol/water partitioning coefficient log P 1.5–8) and total polar surface area (TPSA 25–120 Å) were selected as model bioactives. Partitioning of compounds was evaluated using fluorescence imaging, revealing that compounds preferentially localized at the membrane of the MFGs had the lowest log P (i.e., fisetin and quercetin); whereas compounds that preferentially accumulated in the MFG core were those of highest log P (i.e. eugenol, cholecalcipherol and retinyl acetate). The highest encapsulation efficiency was achieved by retinyl acetate (≥100 %, average log P = 8.0) and the lowest by fisetin (30 %, average log P = 1.5). Machine learning models were used to predict the partitioning of lipophilic molecules into MFGs. The results showed that Random Forest Regression could predict the encapsulation efficiency of the diverse compounds with higher accuracy than multiple linear regression, wherein the compound's log P, TPSA, and membrane binding energy were important features for prediction. The influence of encapsulation process conditions was also evaluated using retinyl acetate. Increased ethanol concentration, incubation time, and temperature positively affected the encapsulation of retinyl acetate. Overall, this study demonstrates that diverse lipophilic food bioactive compounds can be encapsulated in milk fat globules.